You need to have two different arrays to be able to differentiate and add elements withinthem a each user guesses wrong!
ArrayList<Integer> wrongGuesses1= new ArrayList<Integer>();
ArrayList<Integer> wrongGuesses2= new ArrayList<Integer>();
Then figure out in your code who is guessing at that particular instant and if it is wrong then you should add an element to their array respectively!
Although I dont think a user will want to know what their incorrect guesses were, it might just be more efficient to make a counter for the number of wrong guesses there were for each user! :D